Neurostimulation is the therapeutic alteration of activity in the central, peripheral or autonomic nervous systems by means of implantable pulse generators and implanted stimulation devices. Neurostimulation may treat a variety of symptoms or conditions, for example, vagus nerve stimulation (VNS) is an adjunctive treatment for certain types of intractable epilepsy and treatment-resistant depression. A neurostimulator, which is a special kind of implantable pulse generator (IPG), is a battery powered device designed to deliver electrical stimulation to the brain, central and peripheral nervous systems.
The vascular system contains numerous locations within it and in contact with it which are electro-active and present the possibility of therapeutic electrical stimulation. One example of such a location is in the right brachiocephalic vein-Superior Vena Cava (SVC) junction by which runs the right vagus nerve. Stimulation of the vagus nerve has been shown to result in an anti-inflammatory effect and a reduction in sympathetic drive, which is beneficial to patients suffering from a variety of conditions including, but not limited to, heart failure, acute ischemic attack, and atrial and ventricular arrhythmias.
Trans-vascular stimulation electrodes, as one embodiment of implantable stimulation devices, exist for chronic application, for example, for phrenic nerve stimulation, however, most of them are designed for small vessels and cannot be used in large veins. Hence, a system capable of delivering or recording electric fields in a vessel near a neuroactive target location being compatible with large veins would be advantageous.
Trans-vascular stimulation of the vagus nerve has been demonstrated previously with basket catheters. One problem with common expandable basket-style stimulation catheters is that they are designed for acute stimulation and are not appropriate for chronic stimulation.
In a proposed implantable (neuro-)stimulation device, electrodes are positioned intravascularly within a blood vessel (for example, a jugular vein, superior vena cava, or inferior vena cava) and are used to transvascularly stimulate nervous targets located outside the vasculature. For maintaining the electrodes in contact with the blood vessel wall, anchors have been developed. Such anchors include structural features that allow the anchor to radially engage a vessel wall. The anchor may include a band, sleeve, mesh or other framework formed of shape memory materials (for example, nitinol or shape memory polymer) or other non-biodegradable materials like, for example, stainless steel.
One or more of the drawbacks of the state of art (surgical dissection to gain nerve access) may be avoided or at least reduced by use of an implantable (neuro-)stimulation device in the implementation of an intravascular electrode lead which has been developed by the inventors and is subject of the U.S. patent application Ser. No. 14/814,096, which is incorporated in this application in its entirety by reference. Said intravascular electrode lead comprises an electrode shaft; a plurality of filaments being made of a conductive, non-biodegradable material, running in longitudinal direction within the electrode shaft and protruding distally beyond a distal end of the electrode shaft, each filament terminating in at least one electrode element; and a support member being arranged distally from the distal end of the electrode shaft and being dilatable from a compressed state to an radially expanded state, wherein the support member is attached to the filaments and made of a biodegradable material.
The support member may be a radially expandable framework of struts. For example, the support member may have a stent-like or graft stent-like design (also called “stent”). The biodegradable stent is constructed as a support member with inter-woven or mechanically affixed conductive, non-biodegradable filaments. The filaments may be connected to an electrically conducting, biologically compatible tether.
Said intravascular electrode lead relies on a support member, which allows primary fixation and biological encapsulation as a secondary fixation mechanism. The support member, once it is deployed and expanded at the implantation site, and—if equipped with a biodegradable support member—until the support member is completely dissolved, cannot be retracted or explanted.
The nerve bundles that this implantable (neuro-)stimulation device targets have natural physiological variability with respect to their location around the vasculature and cannot be seen via standard medical imaging methods. Thus, it is necessary to ensure that the vascular location of deployment of the known intravascular electrode lead is therapeutically appropriate prior to deployment. In addition, after location of the desired site of deployment, the act of delivery and deployment must not introduce significant stress to the vasculature or uncertainty in the final site of deployment.
Existing solutions for delivery of stents are known. These include balloon-inflatable catheters, where the delivery catheter is comprised of a catheter which includes a lumen along its length, terminating at its distal end in a balloon. A stent rides on this balloon until it reaches the desired delivery location, and the balloon is inflated with liquid via liquid injection into the catheter lumen. In addition, electrically active catheters are known for the purpose of mapping electrical activity in the atria, and for delivering high frequency stimulation for ablation in the atria and renal system. However, there exists no delivery system and corresponding delivery method for the above mentioned intravascular electrode lead, i.e., none of the existing solutions for stent delivery allows for electrical probing of a target location before stent delivery, and none allows for precise delivery of the intravascular electrode lead to the desired vascular location found via probing.
Thus, there is a need for a delivery tool which allows a physician to locate an optimal endovascular neuromodulation location and accurately deliver a neuromodulation stent-based electrode to this location.
The present invention is directed toward overcoming one or more of the above-identified problems.